#include <bits/stdc++.h>
using namespace std;

using point = pair<int, int>;
const vector<int> dx{1, 0, -1, 0}, dy{0, 1, 0, -1};

int main() {
    constexpr int inf = 1e9;
    int h, w, ra, ca, rb, cb;
    cin >> h >> w >> ra >> ca >> rb >> cb;
    ra--; ca--; rb--; cb--;
    vector<string> s(h);
    for (int i = 0; i < h; i++) {
        cin >> s.at(i);
    }
    vector d(h, vector(w, inf)), db(h, vector(w, inf));
    queue<point> q;
    d.at(ra).at(ca) = 0;
    q.emplace(ra, ca);
    while (not q.empty()) {
        auto [x, y] = q.front();
        q.pop();
        for (int i = 0; i < 4; i++) {
            int newx = x + dx.at(i), newy = y + dy.at(i);
            if (s.at(newx).at(newy) == '#') continue;            
            if (d.at(newx).at(newy) != inf) continue;
            d.at(newx).at(newy) = d.at(x).at(y) + 1;
            q.emplace(newx, newy);
        }
    }
    if (d.at(rb).at(cb) == inf) {
        cout << -1 << endl;
        return 0;
    }
    db.at(rb).at(cb) = 0;
    q.emplace(rb, cb);
    while (not q.empty()) {
        auto [x, y] = q.front();
        q.pop();
        for (int i = 0; i < 4; i++) {
            int newx = x + dx.at(i), newy = y + dy.at(i);
            if (s.at(newx).at(newy) == '#') continue;            
            if (db.at(newx).at(newy) != inf) continue;
            db.at(newx).at(newy) = db.at(x).at(y) + 1;
            q.emplace(newx, newy);
        }
    }
    vector<vector<int>> v(h * w);
    for (int i = 0; i < h; i++) {
        for (int j = 0; j < w; j++) {
            if (d.at(i).at(j) == inf or db.at(i).at(j) == inf) continue;
            if (max(d.at(i).at(j), db.at(i).at(j)) <= d.at(rb).at(cb)) {
                v.at(d.at(i).at(j)).push_back(d.at(i).at(j) + db.at(i).at(j));
            }
        }
    }
    int ans = inf;
    for (int i = 0; i < h * w; i++) {
        if (v.at(i).size() <= 1) continue;
        sort(v.at(i).begin(), v.at(i).end());
        ans = min(ans, v.at(i).at(0) + v.at(i).at(1));
    }
    if (ans == inf) {
        cout << -1 << endl;
    } else {
        cout << ans << endl;
    }
}